1. Field of the Invention
The present invention relates to an energy converting device having an eccentric rotor. Particularly, it relates to an energy converting device having an eccentric rotor for converting electric energy into mechanical energy. Its advantages and functions are listed as follows. The rotor structure is simple and its magnetic field is evenly distributed. The magnetic flux variation is close to a sine wave. The generated torque is smoother. It can improve the motor's acceleration and deceleration performance. In addition, it can be seamlessly combined with a cycloidal speed reducer so as to form a cycloidal motor.
2. Description of the Prior Art
The traditional motor can be classified into the radial-flux motor 90 and the axial-flux motor 80 by the flux direction. Most motors belong to the radial-flux motor 90 as illustrated in FIG. 1. Its simplified operation principle can be seen in FIG. 2.
FIG. 3A is a cross-sectional view of a traditional axial flux motor. FIG. 3B is a cross-sectional view of an inner structure of the traditional axial flux motor. Comparing with the radial-flux motor, the axial-flux motor has higher torque density. In addition, because the torque of an axial-flux motor is not related to the rotor thickness (T), the motor's axis-to-diameter ratio (length S over diameter D) is lower. It is suitable for applications where axial space is constrained. The axial-flux motor 80 has been developed to be light-weighted, compact, and having high-torque output. In traditional axial-flux motor the magnets 811 with alternating N-S-N-S arrangement are attached to one face of the rotor 81. When the rotor 81 rotates, the magnetic flux through the coil 821 varies periodically, so that counter-electromotive force is generated.
However, the traditional axial-flux motor still has the following drawbacks and problems.
[1] The magnetic field produced by the magnets on the rotor may not be evenly distributed, because it involves several pieces of magnetic segments or is produced by a magnet magnetized into several alternating N-S-N-S zones.
[2] Analysis of the air-gap flux distribution is complicated. It is inappropriate to use 2-deimentional magnetic analysis tool to analyze its flux distribution. Three-dimensional analysis is required, making its design more costly
[3] When the rotor rotates at a constant speed, the magnetic flux does not vary in a sinusoidal manner.
Besides, referring to FIG. 4, the traditional cycloidal speed reducer 70 includes an eccentric connecting shaft 71 (which is an input shaft for the reducer), an eccentric cycloidal disk 72, a ring gear wheel 73 (or called ring pins), a transmitting pin set 74, and an output disk 75. The transmitting pin set 74 and the output disk 75 are formed as one integral structure. The operation principle is illustrated by FIG. 4. There are four processes shown in FIG. 4 for displacement of a tooth distance. When the eccentric connecting shaft 71 rotates, it drives the eccentric cycloidal disk 72 rotating along the inner edge of the ring gear wheel 73. There are 8 teeth (or protrusions) in the eccentric cycloidal disk 72. There are 9 teeth (or protrusions) in the ring gear wheel 73. Thus, there is one tooth difference. After the eccentric connecting shaft 71 rotated 360 degrees, the eccentric cycloidal disk 72 will rotate to move one-tooth away in the opposite direction. Two reference points A and B are marked in FIG. 4 to explain their different rotational directions and their relative motion. However, the connecting shaft 71 must be driven by an external motor in order to transmit power. The combined volume of the motor (snot shown) and the cycloidal speed reducer may be too large for many applications.